By signing up I agree to the Privacy Policy. I also agree to receive periodic emails with offers and promotional marketing messages from In Touch Weekly.

Woo hoo!

Your life just got exponentially better and more stylish now you've signed up for our newsletter. Fabulousness awaits!

There's one thing Jenelle Evans has made very clear — she will not let anyone cyber bully her man! The Teen Mom 2 star has been very outspoken about her fiancé David Eason's skin condition and she is quick to call out insensitive trolls who makes fun of him for having the disease, and she even tries to spread awareness about it — but what exactly is vitiligo?

It's not a very common disease, as it affects about 0.5 to 1 percent of the world's population. Vitiligo is a disease that occurs when melanocytes — the cells that produce pigment in the skin — die or stop producing melanin, which is what is responsible for giving your skin, hair, and eyes color. The causes can be hereditary, it could be triggered by sunburn or other stress, and it could also be the result of a disorder where your immune system attacks and destroys the melanocytes, according to Mayo Clinic. Symptoms of vitiligo include loss of skin color in patches, premature whitening or graying of hair, and loss of color in the eyeball (retina) or the inside of your mouth.

Judging from photos, David's vitiligo is more prominent in his hands. Back in June, Jenelle posted an adorable photo of her husband-to-be sitting on their couch, sleeping with their seven-month-old daughter Ensley after feeding time. She captioned the sweet daddy-daughter moment "#DadMode gets ya tired sometimes" — but one troll had to ruin it by asking, "Does he have aids whats up with his hand?”

"It's called vitiligo you f--king idiot. It's a loss of pigment in your skin," she clapped back in the comments section. "People are models these days for it. You need to research STDs if you don't know wtf AIDS does to you.... and def don't do that s--t to your skin like that. Maybe you're the one with AIDS and don't even know cuz your [sic] as dumb as a box of rocks my friend.”